Historically, there have been a number of options for the permanent removal of hair. Electrolysis has been the most commonly selected approach, in which an operator, usually an electrologist, attaches an electrode to each individual hair shaft, with the patient typically holding a second electrode. An electrical current is then passed through the hair shaft and the hair follicle through the papilla. This precisely directed current can induce permanent injury in the follicle and papilla, stopping the future production of the hair shaft.
Problems exist with the electrolysis technique, however. The success with which hair is permanently removed varies greatly from patient to patient. Moreover, the process is slow since each hair follicle must be individually treated, and there is some discomfort associated with the electric current.
The removal of hair using lasers is another approach that has found only limited success. Numerous techniques have been taught in the prior art. Each, however, suffers from drawbacks such as poor ultimate success in stopping hair growth even after multiple treatments, excessive injury to the tissue surrounding the hair follicles and papilla, and excessively large and expensive laser systems.
One approach relies on a pulsed laser source and the use of an exogenous absorber. A commercially available hair dye solution is first applied to the skin containing the unwanted hair and allowed to migrate along the hair shafts and into the follicles. The skin is then irradiated with a spot size of approximately 0.5 centimeters using a Q-switched YAG laser, or other short pulsed laser system. The pulse durations used by the lasers tend to be short, 15 nsec for the Q-switched laser. It appears that the sub-microsecond pulse durations shocks the hair follicle, which stops hair production, but only for a limited time. After months, the follicle again begins to produce hair, requiring further treatments or other techniques to yield any lasting success.
Other approaches have been proposed that rely on flashlamps, instead of lasers. This has the advantage of a less expensive, reasonably portable light source, but flashlamps create their own control problems. It is difficult to deliver light from the flashlamp to the skin, so that it must be placed in proximity to the skin. The reflectors that surround the flashlamp and collect the light and direct it to the skin must be precisely built and calibrated. Any error can cause hot spots in the spatial energy distribution. This can lead to under-treatment in some areas and burning in others. Moreover, the bandwidth of the light from these flashlamps is broad, usually including the visible and stretching into the longer infrared wavelengths. These longer wavelengths are well absorbed by water that occupies the skin. Thus, the light from these sources tends to penetrate very poorly, which leads to higher fluence levels to sufficiently treat deeper-lying hair producing structures with the concomitant risk of burning or damaging the skin.
Still other approaches use laser light delivery systems that inject light into only a single hair follicle at a time. These have the advantage of a reduced concern for damaging tissue between hair follicles but have many of the same disadvantages associated with the electrolysis. That is, each individual hair and hair follicle must be separately treated.
Long pulse ruby lasers have recently been used in hair removal. The high energy ruby lasers, however, are generally large, inefficient types of laser light generators, when very long pulses are generated.